Coordination polymers characterized

Hinderberger D, Schmelz O, Rehahn M, Jeschke G (2004) Electrostatic site attachment of divalent counterions to rodlike ruthenium(II) coordination polymers characterized by EPR spectroscopy. Angew Chem Int Ed 43 4616-4621... 

The ligand 2,5-bis(2-pyridyl)pyrazine was used in the synthesis of a range of zinc compounds to contrast with copper coordination polymers prepared with this ligand.169 Three zinc compounds were structurally characterized, [ZnCl2L(DMF)], [Zn3(OAc)6L2], and [Zn3Cl6L3] respectively a distorted square planar monomer, a linear trimer, and a triangular arrangement of zinc centers. 

The structure of coordination polymers formed with 3,6-bis(pyridin-3-yl)-l,2,4,5-tetrazine and zinc salts can be controlled by the choice of alcoholic solvents. Infinite lattice compounds of the form [Zn2L2(N03)4(Me0H)2(//-L)] and [Zn2(/U-L)3(N03)4](CH2C12)2) have been structurally characterized. The former structure shows an alternating single- and double-bridged species whereas the latter exists as a non-interpenetrated ladder complex.273... 

Zinc halide complexes with acetophenone have been structurally characterized and form monomeric or polymeric structural motifs.346 The bromide and iodide derivatives are monomeric and the chloride derivative is a coordination polymer with bridging chlorides. 

As evidence that a monolithiated compound can form an equilibrium with the corresponding dilithiated compound involved, the group of Linti and coworkers crystallograph-ically examined 9,9-dilithiofluorene (45). The molecule is formed when 9-lithiofluorene (44) is dissolved in a THF/benzene mixture by an intermolecular deprotonation yielding 45 and fluorene (43). In spite of the poor solubility of compound 45, which does not allow a characterization by NMR methods, the equilibrium is still on the side of the monolithiated compound (Scheme 16). The crystal structure of compound 45 has been reported and reveals a coordination polymer in the solid state (Figure 13). 

In the solid-state structure of dilithiated fluoranthene (235), generated from 234 in dimethoxyethane at room temperature by Bock and coworkers (Scheme 82), lithium-DME units are capping the naphthalene moiety from both sides of the plane alternatingly (compound 235 forms a coordination polymer in the solid state). The metallic lithium, used for the reaction, was activated by ultrasonic irradiation. Moreover, several structures of related polysodium compounds were also characterized in the solid state . 

The drive for the synthesis and characterization of synthetic coordination polymers was catalyzed by work supported and conducted by the U.S. Air Force in a search for materials which exhibited high thermal stabilities. Attempts to prepare highly stable, tractable coordination polymers were disappointing. Typically, only oligomeric products were formed and the monomeric versions were often more stable than the polymeric versions. 

Preparation and Characterization of Dinuclear Building Blocks and Coordination Polymers... 

This type of dinuclear unit has been reported elsewhere and has been characterized with bis-2-pyridyl-pyrazine or quinoxaline both in Cu [31] and in Ag [32] compounds. However, until now such units have not been used as building blocks (loops) in the construction of coordination polymers, an aspect that is discussed below. Each ligand acts in a bidentate manner with one metal center and as a monodentate system with the other. The two rings that are coordinated to the same metal center are nearly coplanar but the other deviates clearly from this plane. In this way, the structure if this dinuclear unit is very well adapted to the preferred conformation of the free ligand. The relative disposition of the ligands allows the existence of face-to-face n-jt-stacking interactions between the quinoxaline and... 

The zincates K [ZnR(tBuNCH=CHN Bu)] contain the diazabutadiene fragment. They have been made, via a series of radical-anion complexes, from the alkylation of B uN = CHCH = N Bu by potassium in the presence of organozinc compounds, and characterized as THF and Et20 adducts, 70 and 71, respectively. Each forms linear coordination polymers comprising alternate potassium cations and zincate anions held together... 

Leznoff and co-workers reported the structural characterization and the polymorphic nature of a gold(I)-copper(II) coordination polymer, [Cu Au(CN)2 2(dmso)2] 00 [125]. In a green polymorphic form it possessed a 1-D chain structure with five-coordinate copper(II) centers, while a 2-D corrugated sheet structure with six-coordinate copper(II) centers was characterized in the blue polymorph, both of which are linked together to form a 3-D structure via aurophilic interactions. These two polymorphs exhibited virtually identical vapochromic behavior towards water, MeCN, dioxane, dmf, pyridine and ammonia, with the formation of [Cu Au(CN)2 2(solvent)x]oc,. 

In addition to routinely used methods, such as elemental analysis, IR and UV-vis-NIR spectra, thermogravimetry-differential thermal analysis (TG-DTA), single-crystal X-ray diffraction, and gas adsorption, there are some important characterization methods for coordination polymers. 

Most silver acetylides are highly insoluble in standard organic solvents because of the formation of coordination polymers, and this characteristic can cause difficulties with characterization and limit reactivity. This can be overcome by the addition of coordinating donor molecules such as triphenylphosphine that perturb the formation of the polymeric structure.91 In the experience of the authors, however, the addition of such ligands can decrease reactivity. 

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